Although I run straight 50 all the time, I used to run 20/50 but didn't like it in the twin but have never found the need to alter the filtration. I've run thousands of miles across Europe over the decades and had no issues. On a recent trip the only bike in the group that gave any issues was the one with the added paper external filter. It wasn't the filter itself but the mounting, it was in a place where vibes moved it around and whilst static there was clearance, running however closed the clearance up and the pipe fitting wore through. We bypassed it back to standard and it was fine for the remainder of the trip and continues to be so.

Bottom line is doing away with the felt regardless of oil being used won't hurt, neither will it if you leave it in providing you change the oil regularly.